Waterfall Iterative Software Development Process 

Method of developing a program using structured steps to avoid errors

Analysis - 

•  Find out what the program needs to do

•  Can be done through interviews, DIY sessions

•  Software specification document must be created, a legally binding document describing what the software must do and how long the development process will take

•  Scope/mission creep included in software specification, states what will and won’t be involved in the project, meaning developer can reject changes requested by the client if they are outside the scope

•  Analyst convert’s the client’s program description into software specification

Design - 

•  Deciding layout, inputs,outputs and processes

•  Analyst creates the HCI (Human Computer Interface) using wireframes and also creates logic flow structure

•  Methods used can be pseudocode, flow charts, structure diagrams etc

Implementation - 

•  Writing the code up

•  If errors are in design are spotted the design stage may have to be redone

Testing - 

•  Make sure the software works correctly

•  Test tables produced for inputs, expected outputs and actual outputs

Documentation - 

•  Writing up a user guide and technical guide

•  User guide should specify how to actually use the program and any functions the user will need to know

•  Technical guide must specify the minimum hardware requirements (CPU, RAM, Storage, etc) and how to install and run the program

Evaluation - 

•  Review it’s fitness for purpose and whether or not it meets the requirements of the original software specification

•  Used to check for efficient use of coding constructs, how usable it is, how easy to maintain and update the program is, and how robust to errors it is

Maintenance - 

•  Making any required changes/updates

•  3 methods used are Corrective, Adaptive and Perfective

Agile Software Development Process 

• Method of developing software quicker and on a smaller scale

• Breaks development process into smaller steps

• More interaction with the client for changes to be made easier and more frequently

• Not viable for large software projects or certain clients (one-person businesses)

• Sprint - Time critical task that must be completed within a time limit

• Upload deadlines given

• Variable names must be agreed on

Waterfall vs Agile Development  

Requirements Elicitation 

• Involved in Analysis stage, 

• Finding out what you have to do to make the programme meet its requirements

Methods of Requirements Elicitation 

DIY (Do It Yourself) -

• Go out and do the required job yourself, find out what you have to do to actually process job

Interviews -

• Ask those doing the job how it’s done, how current system works

Observations -

• Watching people actually do the job, record steps on how to do it

Inputs Processes and Outputs  

Inputs - 

Anything taken into the program to be processed

Processes - 

What is carried out using the input to change it

Outputs - 

The final result of the program

Types of User  

Novice - 

App users with little to no experience  

Example Website: CBeebies

Intermediate - 

Users that have a good amount of experience, know how to do most things  Example Website: BBC News

Expert - 

Mastered a piece of software, highly able  

Example Website: CERN

Data Types  

Integer - 

Allows to store whole numbers

Real/Double -

 Allows to store decimal numbers

String - 

Allows to store text, letters and characters

Boolean - 

Stores yes or no, true or false value

• Do not start variable names with numbers or include spaces, instead use either underscores or camel hump notation

     Example - 

Underscores - quick_brown_fox

Camel Hump - quickBrownFox

Types of Design Methods  

Wireframe Diagram - 

• Quick sketch of how a programme will look

• Drawn on paper or Microsoft Paint

• Must be labelled

Eg - 

Use a wireframe to design the user-interface of a programme which:

• Asks the user to enter three numbers

• Adds the numbers together together

• Displays the total of the three numbers

Low-Fidelity Prototype - 

• Almost the same as a wireframe, but with more detail

• Usually created in Photoshop or Publisher

Flow Charts - 

• Shows the underlying logic and the flow of information in a programme

• Also show logic gates or decisions

Eg - 

Structure Diagrams - 

• Involved a lot in Higher Course

• Shows you the overall structure of your program

• Inheritance & Modularity

Pseudocode - 

• Way of illustrating program design in text

• Can use plain English

• Only gives the main steps

Types of Maintenance  

Corrective Maintenance - 

• Fixing errors that weren’t discovered during testing but instead during use of the program

• Only maintenance type where the developer is solely responsible for the cost and not the company

Adaptive Maintenance - 

• Is necessary for if the client wants to run their software on a different operating system or device

• Code must be adapted to run on new system

• Usually paid for by client

Perfective Maintenance - 

• Is necessary for when the client requests changes to the program, due to changes in requirements or legal legislation

• Can require whole rework of program which could be expensive

• Paid for in full by the client

Types of Error  

Syntax Error - 

• Error with how the code has been written, mainly spelling mistakes or mistake in structure 

• Can be caught when using a compiler

Execution Error - 

• Error during the running of a program that causes it to crash

• Can be caused by input errors (dividing by zero) or trying to access non-existent data

• Can’t be find during compiling

Logic Error - 

• Errors during running where the programmer has written something wrong 

• For example, dividing an input by the wrong number

• Can't be found during compiling

Golden Rules of Programming

• Use internal commentary

• Use meaningful variable names

• Provide blank lines

• Use indentation

Test Data  

Normal Data - 

• Data that the program is expected to deal with

• Eg. Program expected to take in numbers 1-10, examples of normal test data would be 2, 5, 7

Extreme Data - 

• Data on our outside the boundaries of what the program should be able to deal with

• Eg. Program given data such as 0, 1, 10, 11, 0 and 11 should be rejected

Exceptional Data -

• Data that the program isn’t able to deal with, will likely break the program

• Eg. Program given data such as “TEN” or “CAT”

Test Tables  

• Helps programmer test a full program, records data and results

Example - 

Trace Tables 

• Helps a programmer keep track of a variable’s value in a program

Example - 

• Program to add two numbers between 1 and 10

Dry Runs

• Programmer works through the program on paper to follow code’s logic

• Good for detecting errors in the flow of logic before implementing the program

• Programmer could use a trace table to keep track of variable values during the run

Breakpoints

• Used to put breaks in program code

• When breakpoint triggered the program will stop

• Allows programmer to see variable values at a given point in the code and help to identify logic errors

Watchpoints 

• Breakpoint assigned to a variable

• Program will stop running when the variable reaches a certain value

Data Types 

Integer - 

• Positive and negative numbers

Real/Double -

• Numbers of currency, fractions or decimals

String -

• Words or characters

Boolean - 

• True or false value

Loops

For Loop -

• Loops for specified amount of times

Eg - 

For counter = 0 to 3 

total = total + 1

Next

While Loop - 

• Loops until a certain requirement is met

Eg - 

While input = 3

total = total + 3

End While

If Loop -

• Loops once when a certain requirement is met

Eg - 

If counter = 3

total = total + 3

End If

Parameter Passing and Modularity

Modularity - 

• Breaks down main program into smaller sub-programs

• Means modules can be tested independently

• Can mirror structure diagram

Parameter Passing - 

• Formal parameters appear in call statement

• Actual parameters is in your module

• Both must be in the same order between call statement and private sub to prevent type mismatches

ByRef and ByVal

ByRef - 

• Passing the actual information on 

• Can change original value

ByVal - 

• Passes on copy of information,

• Original value does not change, 

• Uses up more performance / storage due to requiring more file size

Records 

• Multi-slot array

• Can hold multiple data types

• Must be created completely separately from a program and be called later on

Reading from File

In Exam - 

read in from file

age = received from file

name = received from file

close file

Software Evaluation

Fitness for Purpose - 

• Making sure that the finished product meets the requirements of the original software specification

• Broken down into different criteria

Efficient Use of Coding Constructs - 

• Make good use of system resources, and code should be written as efficiently as possible

• Eg - Using arrays, loops, pre-defined functions

Usability - 

• How easy it is for somebody to use a program

• Make sure the program is as easy to learn as possible

• Eg - Objects / buttons should be clearly labelled, error messages should be easily understood, must be suitable for all different levels of user

Maintainability - 

• How easy the program is to work on and update

• Eg - Using modular coding through sub-programs, meaningful variable names, internal commentary, white space, indentation

Robustness - 

• How safe and protected the program is to errors

• Eg - Should be able to cope with invalid inputs, should report errors clearly

Translators 

Data Structures

Arrays - 

Arrays are a data structure that can store multiple values of the same data type i.e.

 integer

Parallel Arrays - 

Parallel arrays are multiple arrays all holding data relevant to each other i.e forename

and surname

Records - 

A record structure is used to store multiple data types but only one of each i.e 

One forename and one age

Array of Records - 

An array of records structure is used to store multiple of different data types i.e.

multiple forenames and multiple ages